The invention relates to a turbo-engine with transonically traversed stages, particularly a gas turbine with a stationary forward-guiding grid.
In the case of transonically traversed gas turbines [flow-in speed at the guide wheel in the subsonic range; median flow-out speed at the guide wheel trailing edge in the transonic range (M&gt;0.8)], one or several compression waves occur in the case of a flow-off at high Mach numbers at the trailing edge of the guide wheel. These compression waves with the blade pitch generate periodic pressure gradients that are many times larger than in the subsonic range (M&lt;0.8).
If hollow spaces are located outside the flow duct of the gas turbine, a flowing-in of the gas into the hollow spaces takes place at points of high pressure, and a flowing-out takes place at points of low pressure. In every section between respective blades, a circulating flow occurs at the radially outside and inside edge of the flow duct. This intensely interferes wtih the main flow, increases losses and impairs the efficiency of the gas turbine. Another disadvantage is that, when hot gas flows into the hollow spaces, the temperature of the components is increased, whereby the stability and the durability is reduced.
It is an objective of the invention to eliminate the above-mentioned disadvantages that occur in the case of a turbo-engine of the above-mentioned type and particularly to prevent or minimize a circulating flow between the blades in each between blade section at the trailing edge of the forward-guiding grid.
According to the invention, this objective is achieved by the fact that a compensating arrangement is provided over the circumference behind the guiding grid at the hub and/or housing, for the pressure compensation of pressure gradients occurring as a result of compression waves at the outlet edge of the forward-guiding grid.
This arrangement of the invention has the significant advantage that the circulating flows that occur as a result of the compression waves are prevented, and in this way, flow losses are reduced and the thermal stress to components caused by hot gas penetrating into the hollow spaces is reduced.
The compensating arrangement is preferably designed as at least one steadying or balancing chamber extending over the circumference on the side of the hub which has a circumferential opening in the direction of the rotor disk that follows, which is covered by a radially operating sealing flange of the rotor disk.
The sealing flange is advantageously developed as a double circumferential seal, each of the two circumferential seals being developed as a labyrinth seal. These measures prevent that hot gas penetrates through the gap between the rotating and the stationary parts into the hollow spaces that are located radially on the inside, and that the resulting circulating flow interferes with the main flow.
Advantageous measures may also be provided at stationary parts for the purpose of preventing or minimizing the circulating flow according to certain preferred embodiments of the invention. In particular, annuluses arranged in the housing are developed with a connection to the main flow by means of a blocking element as the throttling point.
The annulus is filled with a filler, such as metallic or mineral wool, fibers, tissue, foam. Although such loose closing or blocking of the annulus permits a pressure and temperature compensation, it prevents a significant gas flow.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.